The present invention concerns a process for imparting surface structures to wood-cement boards which during the cement hardening are pressed in a batch-press and then are kept in a clamping apparatus in the pressed state for a substantial length of time until the cement has hardened so that swelling of the wood fibers no longer is possible.
It is known in the prior art manufacture of asbestos-cement boards to provide the oiled partition plates of a press stack with surface structures which are transferred to the boards during pressing. Contrary to the case for wood-cement boards, asbestos-cement boards however can be stored in the unclamped state directly after pressing because swelling or other deformations cannot take place due to the nature of this material.
If the prior art process used for asbestos-cement boards were to be applied to wood-cement boards, the structured plates would have to remain during the entire clamping time within the clamped stack until hardening of the cement. As a result an extraordinarily large number of structured partition plates is required for manufacturing on a substantial scale, such structuring therefore requiring inadmissible costs for its implementation, the more so that structured plates of the cited kind can only be manufactured at appreciable expense.
It is further known from the manufacture of asbestos-cement boards to impart the structure using calendering rolls of which the surface is suitably profiled, the asbestos-cement boards being made to pass in their fresh state between the calender rolls. However this is possible only where subsequent pressing is not needed, as might be the case for certain asbestos-cement boards. As regards wood-cement boards on the other hand, pressing must be performed, as without it the required strength of these boards cannot be obtained. In the course of such pressing therefore a structure applied in the fresh state would be forced out again.